diff -up megaglest-3.12.0/source/shared_lib/CMakeLists.txt.orig megaglest-3.12.0/source/shared_lib/CMakeLists.txt
--- megaglest-3.12.0/source/shared_lib/CMakeLists.txt.orig	2016-06-24 07:40:18.704508869 -0300
+++ megaglest-3.12.0/source/shared_lib/CMakeLists.txt	2016-06-24 07:40:49.689510832 -0300
@@ -76,7 +76,7 @@ IF(BUILD_MEGAGLEST_MODEL_VIEWER OR BUILD
 	FIND_PACKAGE(OpenGL REQUIRED)
 	INCLUDE_DIRECTORIES(${OPENGL_INCLUDE_DIR})
 	IF(UNIX)
-		SET(EXTERNAL_LIBS ${EXTERNAL_LIBS} ${OPENGL_LIBRARY})
+		SET(EXTERNAL_LIBS ${EXTERNAL_LIBS} ${OPENGL_LIBRARY} -lX11)
 	ENDIF()
 
 	FIND_PACKAGE(X11 REQUIRED)
